We have Zimbra mail server installed as corporate mail server. We are using the same for last couple of years and facing no issues. Earlier we were using Zimbra based mail server with windows as OS in users systems. Now we are looking to move towards Ubuntu as OS. We have Sonicwall NSA2400 firewall installed at gateway.
The problem we are facing is when we are sending mails using thunderbird mail client using Ubuntu as OS, connection with mail server fails. If we are using the same with Windows as OS and MS outlook express as mail client its working fine without any issue.
Is there any change needs to be made in config file or any system file in Zimbra mail server to make it compatible with Ubuntu as OS
Please help in resolving the issue.